The laser fire of the Colonial Vipers makes a different sound than they do in the rest of the series.
Not only is it the last episode of the series, but it serves as the return of the Cylons, who were absent during many of the previous episodes.
Last show of the series.
Apollo reveals that the Galactica was launched "over 500 yahren ago". According to BattlestarWiki, fans have established a "yahren" (equivalent to a Colonial year) as being equivalent to approximately 250 Earth days, or a little more than 2/3 of an Earth year. That still makes the Galactica an extremely old ship at over 340 Earth years old. In terms of Earth history, it would be like continuing to use a warship from about 1680 C.E.